Hysteretic Behaviour of Stockbridge Dampers: Modelling and Parameter Identification

Abstract

Stockbridge dampers are widely used to mitigate the vortex-induced vibrations of overhead electrical line conductors and of many other cable or cable-like structures exposed to the action of wind. Aim of this work is to develop a simple, but accurate, mechanical model of a Stockbridge damper to use in the assessment of such structures vibrations. The model is based on a beam-like description of the messenger cable and on a nonlinear formulation of the cross sections cyclic bending behaviour. At the cross-sectional level, the mechanical behaviour of the messenger cable is reproduced with the classic Bouc-Wen hysteretic model, which has been recognized as adequate to represent the local behaviour mainly controlled by interwire sliding processes. The Bouc-Wen model parameters are identified from experimental results available in literature and used at the local (cross-sectional) level to characterize the mechanical behaviour of the messenger cable. The descending global behaviour of the Stockbridge damper compares very favourably with the experimental results in terms of the impedance function at the clamp and allows for the confident use of the proposed model inside the assessing process of full power lines. The important role of the end zones of the messenger cable is highlighted. In these zones, a boundary layer like transition is found to occur for the bending stiffness of the messenger cable cross section. This largely affects the global behaviour of the Stockbridge damper. The length of these zones complements the model parameters.

A Stochastic and Continuous Model of Aeolian Vibrations of Conductors Equipped With Stockbridge Dampers

“…The most common type of Stockbridge dampers is made of a metallic clamp, a short metallic strand, also known as "messenger cable," with two inertial bodies attached at its end-sections [10,9]. The clamp is rigidly attached to the messenger cable and allows connecting the damping device along the span of the OHL conductor.…”

“…Whenever the clamp undergoes a vertical translation, the two sides of the messenger cables behave as uncoupled flexible cantilevers with lumped translational and rotational masses attached at their ends. Differently than classic linear tuned mass dampers [4], Stockbridge dampers are characterized by a markedly hysteretic dynamic behavior due to the frictional dissipation mechanisms activated by the bending of the messenger cable [28,9].…”

“…By denoting as v = v (t) the vertical displacement of the tip of the messenger cable with respect to the clamp, the force F d exerted by the damper on the cable (also see Eq. (1)) can be expressed as [9]:…”

“…Nonlinear passive control devices such as Stockbridge dampers, hence, are often installed along the line spans to reduce the vibration severity (e.g. [9]).…”

Desarrollo de un dispositivo para mitigación de vibraciones para sistemas de catenaria rígida = Development of a vibration mitigation device for rigid catenary systems

“…Estos amortiguadores están compuestos por una masa y un cable flexible que actuará como resorte de flexión [47,50,134,52].…”